THERESA May has made clear the UK will “never” accept a so-called customs back-stop plan, which applied only to Northern Ireland as proposed by the EU, as this would create an internal border and undermine the Union of the United Kingdom. . http://www.heraldscotland.com/news/16279134.May_tells_Barnier_UK_will__never__accept_customs_border_between_N_Ireland_and_rest_of_UK/